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RPi + OSMC Do I need to ground my APA102 lights in top left corner if I already grounded at bottom right corner

Discussion in 'Hardware Support' started by osorocks, 12 February 2019.

  1. osorocks

    osorocks New Member

    Messages:
    15
    Hardware:
    RPi3
    My Pi and Ambilight set up is finished, I got the rainbow swirl and everything.

    However my lights are flickering a bit sometimes.

    I used 158 APA102 lights for my tv (10 amps), for a length of 19 feet (82 inch tv). I used 17 awg primary wire (IS PRIMARY WIRE OK? it said on packaging for automotive use)

    Currently I have the beginning and end strip's GND and 5V (all at the BOTTOM RIGHT) linked to a terminal strip and then linked to the 5V 15 A power supply.

    I figured since there are 9 feet of LED STRIPS going clockwise from BOTTOM RIGHT and counterclockwise from BOTTOM RIGHT, that I would need to wire the 5V from led at TOP LEFT to the positive power supply and GND to the negative power supply terminal strip.

    I still have one more question before I try this.Since at the BOTTOM RIGHT I have a male to female connected to the gpio pin 6 for grounding, will I also have to ground the TOP LEFT corner? Or is it like DI/CI CO/DO where I only need to have the signal go one direction.

    My main questions are underlined.

    In the video. white circle is BOTTOM RIGHT and yellow circle is TOP LEFT (ssorry for mixmatching)
    You can see flicker near the white circle in this video
    https://vimeo.com/user95009912/review/316703000/59e07d3880
     
  2. Akriss

    Akriss Active Member

    Messages:
    496
    Hardware:
    RPi1/Zero, RPi2, RPi3, 32/64bit, +Arduino, +nodeMCU/ESP8266
    Wire is usually universal, the gauge is what matters. automotive wire is usually stranded wire as opposed to solid wire. stranded wire is flexible, solid wire not so much. In short it's ok.

    No, one ground wire is fine. Be sure that it's a good connection, loose ground (or any) wire can cause flicker.

    Some things come to mind in troubleshooting:
    Very long runs of wire between the led strip and the driver can act as a antenna and pick up stray signals that interfere with the led signal.
    Most micro controllers output 3.3v signals. The led strip are expecting a signal closer to 5v. And if using long runs of wire. Long wire add resistance and a subsequent voltage drop to the signal. A level shifter can be used to bump up the 3.3v signal to 5v.
    Having a strong signal to the leds can overcome interference.
    Lots of good posts on this forum on how to hook up a level shifter. I prefer 74AHCT125 level shifter.

    Hope its of help.
     
  3. osorocks

    osorocks New Member

    Messages:
    15
    Hardware:
    RPi3
    Can you link me a guide to installing a level shifter with raspberry pi and apa102?
     
  4. Akriss

    Akriss Active Member

    Messages:
    496
    Hardware:
    RPi1/Zero, RPi2, RPi3, 32/64bit, +Arduino, +nodeMCU/ESP8266
    A very good guide Is Adfruits guide HERE.

    This guide is for different leds. But has good info. Here


    Hope it helps.
     
    Last edited: 12 February 2019
  5. osorocks

    osorocks New Member

    Messages:
    15
    Hardware:
    RPi3
    I am not quite sure I understand on the guides.

    So for my Rpi 3 and apa102 , I need to "level shift" gpio pins into CI/CO,DI/DO. When you are referring to signals, is it the signals that communicate what color each led turns?

    Do I still need to run another wire across the tv for 5v and gnd?

    I saw I needed a breadboard, is there a specific one i need?
     
  6. Akriss

    Akriss Active Member

    Messages:
    496
    Hardware:
    RPi1/Zero, RPi2, RPi3, 32/64bit, +Arduino, +nodeMCU/ESP8266
    Yes.

    Here it a picture I came upon that should help.
    raspberry_pi_power-2-batts.png
    The battery can be seen as any power supply.

    No, just make sure it has a pitch (hole spacing distance) of 0.1, most are.

    A good post is https://hyperion-project.org/threads/level-shifter.623/ for good info.

    A photo of one I cobbled together.
    [​IMG]

    Hope its of help.
     
    Last edited: 13 February 2019
  7. MikeDC

    MikeDC New Member

    Messages:
    7
    Hardware:
    RPi1/Zero, RPi2, RPi3, +Arduino, +PhilipsHue
    myself, i supplied 5v at each corner of my tv as i was suffering voltage drop on the long lengths of leds. it was noticible with the odd white flicker but more obvious in the color of the leds that i had an issue.
    the leds changed shade the further it got from the supply when i fed it 5v from only one end.
    now its fed at all 4 corners i have consistent colors and no flicker.
     
  8. osorocks

    osorocks New Member

    Messages:
    15
    Hardware:
    RPi3
    can you show me how you did it with a picture or something thank you
     
  9. osorocks

    osorocks New Member

    Messages:
    15
    Hardware:
    RPi3
    And the AWG wire used.
     
  10. MikeDC

    MikeDC New Member

    Messages:
    7
    Hardware:
    RPi1/Zero, RPi2, RPi3, +Arduino, +PhilipsHue
    you can calculate the wire size required based on how many LED's you have but i didnt mine is probably over sized :)

    All wire I used was silicone wire which is super flexible AWG18(7Amp) and AWG14(18Amp)

    On the back of each LED strip I took a length of AWG 18 to the center of the TV for both 5V and GND from only one end of each strip
    it looks like 2 big X's across the back of the TV one Red one Black

    Where they meet in the middle of the TV I joined all the Reds together and all the Blacks together.
    From the middle of the TV to the PSU I used 14 AWG

    I then used AWG 18 to join the corners together on the front side of the LED strip so its a complete circle round the TV for both 5V and GND

    Hope this helps
     
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